Specific antigenic fractions of T. spiralis larvae will be tested with splenic T-cells to determine those capable of causing specific stimulation in in vitro blastogenic studies. Active fractions will be tested by footpad injections of mice for their sensitizing properties as measured by their effectiveness in causing expulsion of adult worms of T. spiralis, etc. Whole-body, X-irradiation of mice will be used along with reconstitution with normal bone marrow cells, etc., to shed light on the T-cell dependency of reactions that ultimately cause expulsion of T. spiralis. BIBLIOGRAPHIC REFERENCES: Larsh, J.E., Jr., and N.F. Weatherly. 1975. Cell-mediated immunity against certain parasitic worms. In Ben Dawe's ed. Advances in Parasitology. Volume 13, pp. 183-222. Academic Press. London. Race, G.J., Larsh, J.E., Jr., Martin, J.H., and Weatherly, N.F. 1974. Light and electron microscopy of the intestinal tissue of mice parasitized by Trichinella spiralis (pp. 75-100). In trichinellosis (C.W. Kim, ed.), In text Educational Publishers, New York.